﻿using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls.Primitives;
using System.Windows.Interop;

namespace Resource.Controls
{
    public class PopupNonTopmost : Popup
    {
        public PopupNonTopmost()
        {
            Window mainWin = Application.Current.MainWindow;
            mainWin.Deactivated += MainWinDeactivated;
        }

        public static DependencyProperty TopmostProperty = Window.TopmostProperty.AddOwner(typeof(PopupNonTopmost), new FrameworkPropertyMetadata(false, OnTopmostChanged));
        public bool Topmost
        {
            get { return (bool)GetValue(TopmostProperty); }
            set { SetValue(TopmostProperty, value); }
        }
        private static void OnTopmostChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
        {
            (obj as PopupNonTopmost).UpdateWindow();
        }

        void MainWinDeactivated(object sender, EventArgs e)
        {
            IsOpen = false;
        }

        protected override void OnOpened(EventArgs e)
        {
            UpdateWindow();
        }

        private void UpdateWindow()
        {
            Window mainWin = Application.Current.MainWindow;
            var fromVisual = (HwndSource)PresentationSource.FromVisual(this.Child);
            if (!mainWin.IsActive && fromVisual != null)
            {
                IntPtr hwnd = fromVisual.Handle;
                RECT rect;
                if (GetWindowRect(hwnd, out rect))
                {
                    SetWindowPos(hwnd, -2, rect.Left, rect.Top, (int)this.Width, (int)this.Height, 0);
                }
            }
        }

        #region P/Invoke imports & definitions

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
        }

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);

        [DllImport("user32", EntryPoint = "SetWindowPos")]
        private static extern int SetWindowPos(IntPtr hWnd, int hwndInsertAfter, int x, int y, int cx, int cy, int wFlags);

        #endregion
    }
}
